This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The hypothesis of this study is that HCV/HIV infected subjects will increase viral load during effective antiretroviral therapy and viral kinetic modeling will demonstrate that the increase in HCV viral load is directly related to to increased viral production. The primary objective is to characterize early/late HCV viral kinetics as well as the prevalence, significance, and pathogenesis of HCV viral load increase.